1. Field of the Invention
The present invention relates generally to a magnetic disk drive, and more particularly to a stopper mechanism for limiting the swing range of a head actuator in the magnetic disk drive.
2. Description of the Related Art
In a magnetic disk drive, data is read/written on a data zone of a rotating magnetic disk by a magnetic head mounted on the front end portion of a head actuator.
An actuator stopper is provided to limit the swing range of a rotary head actuator. The actuator stopper serves to prevent the magnetic head mounted on the front end portion of the head actuator from leaving the magnetic disk, for example, when the head actuator runs away for any reason. Further, a starting point of servo track writing is defined by the position of the actuator stopper.
In an actuator stopper mechanism or a conventional magnetic disk drive, an inner stopper and an outer stopper are fixed by bonding or press-fitting to a magnetic circuit fixed to a base of the magnetic disk drive, and a coil supporting portion of a head actuator is made to contact with the inner stopper or the outer stopper to thereby limit the swing range of the head actuator. Another magnetic disk drive known in recent years is such that both the stoppers are not provided in the magnetic circuit, but the outer stopper is provided in the magnetic circuit and the inner stopper is fixed to the base so as to abut against the front end portion of an actuator arm.
A rubber stop is mounted on the front end portion of each of the inner stopper and the outer stopper. The rubber stop serves to reduce an impact acceleration when the head actuator runs away for any reason to collide with the inner stopper or the outer stopper, thereby preventing a blemish on the surface of the magnetic disk due to the possibility that the magnetic head mounted on the head actuator may tap on the surface of the magnetic disk.
As one means for increasing a recording capacity in the magnetic disk drive, it is known to widen the data zone of the magnetic disk. The data zone varies with a position tolerance of the inner stopper or the outer stopper. Accordingly, the data zone can be widened by minimizing the position tolerance of the stoppers. In the magnetic disk drive wherein both the inner stopper and the outer stopper are provided in the magnetic circuit, the data zone is influenced not only by the position tolerance of the inner stopper and the outer stopper but also by the position tolerance of the magnetic circuit, because the magnetic circuit is fixed to the base of the magnetic disk drive. In consideration of this, the inner stopper only is located so as to abut against the actuator arm in the vicinity of its front end portion as mentioned above to thereby eliminate the position tolerance of the magnetic circuit.
In the case where both the stoppers are provided in the magnetic circuit, the position tolerance of the stoppers is amplified at the position of the magnetic head because the distance from the center of rotation of the head actuator to the magnetic head is relatively long. However, this problem can be prevented by locating the inner stopper in the vicinity of the front end portion of the actuator arm. In such a conventional magnetic disk drive, however, only the inner stopper is located in the vicinity of the front end portion of the actuator arm, but the outer stopper is located yet in the magnetic circuit fixed to the base.
There may be two reasons why the outer stopper is located yet in the magnetic circuit. Firstly, if the outer stopper is fixed to the base so as to abut against the actuator arm in the vicinity of its front end portion as similar to the inner stopper, the actuator arm is blocked by the outer stopper in loading the magnetic head over the magnetic disk, so that the magnetic head cannot be loaded over the magnetic disk. Secondly, if the outer stopper is located in the vicinity of the front end portion of the actuator arm after loading the magnetic head over the magnetic disk, the outer stopper lies under the magnetic disk, so that it is difficult to fix the outer stopper by a screw or the like in assembling the magnetic disk drive.